U.S. patent number 6,944,316 [Application Number 10/175,148] was granted by the patent office on 2005-09-13 for motility analysis within a gastrointestinal tract.
This patent grant is currently assigned to Given Imaging LTD. Invention is credited to Arkady Glukhovsky, Gavriel Meron, Ofra Zinati.
United States Patent |
6,944,316 |
Glukhovsky , et al. |
September 13, 2005 |
Motility analysis within a gastrointestinal tract
Abstract
A system and method for measuring and analyzing motility within
a body lumen such as the gastrointestinal (GI) tract, where an in
vivo imaging device such as a capsule captures images and transmits
the images to a processor, which calculates the motility of the
device based on comparison of the images. Preferably, the processor
compares the intensity of pairs of images or of elements of pairs
of images, generates a variance for the compared images, and
calculates the motility of the imaging device from the variances.
The motility data may be presented to a user in various manners;
for example, a plot of motility over time may be generated, or
indications of low motility may be presented to the user of the
system.
Inventors: |
Glukhovsky; Arkady (Santa
Clarita, CA), Meron; Gavriel (Petach Tikva, IL),
Zinati; Ofra (Haifa, IL) |
Assignee: |
Given Imaging LTD (Yoqnearn
Ilite, IL)
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Family
ID: |
23153631 |
Appl.
No.: |
10/175,148 |
Filed: |
June 20, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCTIL0200386 |
May 19, 2002 |
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Current U.S.
Class: |
382/107; 382/128;
600/117; 600/160 |
Current CPC
Class: |
A61B
1/042 (20130101); A61B 1/041 (20130101) |
Current International
Class: |
A61B
1/04 (20060101); G06K 009/00 (); A61B 001/04 () |
Field of
Search: |
;382/107,128
;348/65,77,85 ;600/109,117,160 ;128/922 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Rowell, Nancy D., Endoscopes Go Wireless, Biophotonics in Action,
Photonics Spectra, Mar. 2001, pp 60, 62..
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Primary Examiner: Johns; Andrew W.
Attorney, Agent or Firm: Pearl Cohen Zedek Laizer LLP
Parent Case Text
The present application claims benefit from prior U.S. Provisional
Application Ser. No. 60/299,178 entitled "MOTILITY ANALYSIS WITHIN
A GASTROINTESTINAL TRACT" filed on Jun. 20, 2001 and is a
continuation International Application No. PCT/IL02/00386 entitled
"MOTILITY ANALYSIS WITHIN A GASTROINTESTINAL TRACT" filed on May
19, 2002.
Claims
What is claimed is:
1. A method for measuring and analyzing motility within a body
lumen, the method comprising the steps of: accepting images
acquired by a vehicle disposed within said body lumen; and
calculating a motility of the vehicle within said body lumen based
on comparison of said accepted images.
2. The method as in claim 1, wherein said vehicle is a capsule.
3. The method as in claim 1, wherein said motility is relative
motility.
4. The method as in claim 1, wherein said motility is absolute
motility.
5. The method as in claim 1, wherein said comparison is a
comparison of image intensity.
6. The method as in claim 1, further comprising the steps of:
comparing two images; generating a variance for the two images; and
repeating the comparing and variance generating steps for a
plurality of image pairs to generate a series of variance
values.
7. The method as in claim 1, wherein the step of comparing the
images includes, for a pair of images to be compared, at least the
steps of: dividing each image into sections; comparing
corresponding sections of the images to produce a matrix of
difference values; and calculating a variance between the two
images, the variance based on a function of the matrix.
8. The method as in claim 1 wherein said vehicle transmits image
data from a gastrointestinal tract.
9. The method as in claim 1, comprising displaying an indication of
motility.
10. The method as in claim 1, comprising creating a plot which
displays motility as a function of time.
11. The method as in claim 10, comprising: allowing a user to
indicate a point on the plot; and displaying to the user a set of
images corresponding to said point on the plot.
12. The method as in claim 1, comprising the step of providing a
visual indication of which of the images correspond to a motility
which is below a threshold.
13. A system for measuring and analyzing motility within a body
lumen, the system comprising: an image storage memory accepting
images acquired by a vehicle disposed within said body lumen; an
image processor calculating a motility of the vehicle within said
body lumen based on comparison of properties of said accepted
images; and a display on which a plot of said motility as a
function of time is displayed.
14. The system as in claim 13, wherein said vehicle is a
swallowable vehicle.
15. The system as in claim 13, wherein said vehicle is a
capsule.
16. The system as in claim 13, wherein said motility is relative
motility.
17. The system as in claim 13, wherein said motility is absolute
motility.
18. The system as in claim 13, wherein said comparison is a
comparison of image intensity.
19. The system as in claim 13, comprising a processor performing
the steps of: comparing two images; generating a variance for the
two images; and repeating the comparing and variance generating
steps for a plurality of image pairs to generate a series of
variance values.
20. The system as in claim 13, wherein said vehicle includes a
transmitter.
21. The system as in claim 13, comprising: an input device
accepting an indication from a user of a point on the plot, wherein
in response to said indication a set of images corresponding to
said point on the plot is displayed on said display.
22. A system for measuring and analyzing motility within a body
lumen, the system comprising: an image storage means for accepting
images acquired by an image capture means disposed within said body
lumen; an image processor means for calculating a motility of the
image capture means within said body lumen based on comparison of
properties of said accepted images; and a display on which a plot
of said motility as a function of time is displayed.
23. The system as in claim 22, wherein said image capture means is
disposed within a swallowable vehicle.
24. The system as in claim 22, wherein said image capture means is
disposed within a capsule.
25. The system as in claim 22, wherein said motility is relative
motility.
26. The system as in claim 22, wherein said motility is absolute
motility.
27. The system as in claim 22, wherein said comparison is a
comparison of image intensity.
28. The system as in claim 22, comprising a processing means for:
comparing two images; generating a variance for the two images; and
repeating, for a plurality of image pairs, comparing and generating
a variance, to generate a series of variance values.
29. The system as in claim 22, wherein said image capture means
includes a transmitting means.
30. The system as in claim 22, comprising: an input means accepting
an indication from a user of a point on the plot;
wherein in response to said indication a set of images
corresponding to said point on the plot is displayed on said
display means.
31. A method for measuring and analyzing motility within a body
lumen, the method comprising: accepting images acquired by a
vehicle disposed within said body lumen; comparing two images;
generating a variance for the two images; repeating the comparing
and variance generating steps for a plurality of image pairs to
generate a series of variance values; calculating a motility of
said vehicle within said body lumen based on said series of
variance values.
32. A method for measuring and analyzing motility within a body
lumen, the method comprising: accepting images acquired by a
capsule disposed within said body lumen; comparing pairs of said
images; calculating a motility of said capsule within said body
lumen based on said comparisons; and creating a plot which displays
motility as a function of time.
33. A method for measuring and analyzing motility within a body
lumen, the method comprising: accepting images acquired by a
vehicle disposed within said body lumen; comparing two images;
generating a variance for the two images; repeating the comparing
and variance generating, steps for a plurality of image pairs to
generate a series of variance values; calculating a motility of
said vehicle within said body lumen; and
providing an indication of motility.
34. A method for measuring and analyzing motility within a body
lumen, the method comprising: accepting images acquired by a
capsule disposed within said body lumen; comparing a set of images;
generating a variance for the set of images; repeating the
comparing and variance generating steps to generate a series of
variance values; calculating a motility of said capsule within said
body lumen; and
providing an indication of motility of the capsule.
35. A method for measuring and analyzing motility within a body
lumen, the method comprising: accepting images acquired by a
capsule disposed within said body lumen; and calculating a motility
of the capsule within said body lumen based on comparison of said
accepted images.
36. A method for determining at least one condition in a GI tract
comprising the steps of: calculating a motility of a device within
the GI tract; creating a spectral analysis of said motility;
examining the spectral analysis for at least one parameter;
comparing said parameter to a reference; and determining a
condition, if any, in the GI tract based on the comparison.
37. The method according to claim 36 further comprising creating a
plot, which displays motility as a function of time.
38. The method according to claim 36 comprising accepting images
acquired by the device.
39. The method according to claim 36 wherein calculating the
motility includes at least comparing images accepted from the
device.
40. The method according to claim 36 wherein calculating the
motility includes at least monitoring the intensity of RF signals
transmitted from a capsule disposed within said GI tract.
41. The method according to claim 36, wherein said device is a
capsule.
42. A system for determining at least one condition in a GI tract
the system comprising: a receiver capable of receiving signals from
a device within the GI tract; and a controller capable of:
calculating a motility of the device; creating a spectral analysis
of said motility; examining the spectral analysis for at least one
parameter; comparing said parameter to a reference; and determining
a condition, if any, in the GI tract, based on the comparison.
43. The system according to claim 42 wherein the controller is
capable of creating a plot which displays motility as a function of
time.
44. The system according to claim 42 wherein calculating the
motility includes at least comparing images accepted from the
device.
45. The system according to claim 42 wherein said device is a
capsule.
Description
FIELD OF THE INVENTION
The present invention relates to a method and system for analysis
of motility within a body lumen, such as within the
gastrointestinal (GI) tract.
BACKGROUND OF THE INVENTION
Normal peristalsis within a GI tract is responsible for
transporting swallowed food and aiding in digestion and eventual
evacuation. Peristalsis results in pressure waves moving along the
GI tract, in turn resulting in the motility of a bolus within the
GI tract. Thus, changes in motility along the GI tract may indicate
normal conditions such as food passing from one section of the GI
tract to another (such as passage from the stomach to the small
intestine or passage from the small intestine to the large
intestine). Certain pathological conditions can alter the normal
motility within the GI tract. Low motility may be caused by an
obstruction or blockage or by other pathological conditions. It is
often difficult to detect areas of low or abnormal motility within
the GI tract, since these areas may be in difficult to reach
locations. It is difficult to "see" inside the tract, especially in
sections that are hard to reach via conventional methods, such as
the small intestines. Motility is the result of complex
neuro-physiological processes. Motility disorders may be caused by
nervous disorders, and may not necessarily be visible as, for
example, physiological changes in the intestinal tissue.
Various in vivo measurement systems for examining a body lumen are
known in the art. A commonly known and used type of system is an
endoscope. Endoscopes are devices which include a tube (either
rigid or flexible) and an optical system, and which are introduced
into the body to view the interior. The range of endoscopes--the
portion of the GI tract, which endoscopes are capable of
viewing--is limited. Endoscopes are usually not helpful in
providing information on GI tract motility. Probes, such as
pressure probes, may be used to measure peristaltic pressure waves.
Other systems that may be used for obtaining information on GI
tract motility include dissolvable vehicles containing non
dissolving markers that are visible by X-ray. The vehicle is
ingested and the progression of the markers, which are released in
the GI tract once the vehicle is dissolved, can be followed by
X-ray. This method, however, can not be used for continuous
monitoring and also exposes the patient to hazardous X-rays.
A non hazardous system and method for monitoring and/or analyzing
movement along the entire GI tract is needed, inter alia, for
facilitating the understanding of GI tract motility and for
expanding diagnostic (and perhaps therapeutic) possibilities in the
GI tract.
SUMMARY OF THE INVENTION
An exemplary embodiment of the system and method of the present
invention measures and analyzes motility within a body lumen such
as the GI tract. In another embodiment of the invention a method is
provided for diagnosis of in vivo conditions in the GI tract of a
patient. In one embodiment an in vivo imaging device such as an
ingestible imaging capsule captures images and transmits the images
to a processor, which calculates the motility of the device based
on comparison of the images. In one embodiment the processor
compares the intensity of pairs of images or of elements of pairs
of images, generates an average difference for the compared images,
and calculates the motility of the imaging device from the average
differences. In other embodiments indicators, such as radio
frequency (RF) signals, strain gauges, velocity meters or
accelerometers may be used to calculate the motility of a device.
In another embodiment a geometrical location or in vivo position of
the device may be determined for later calculation of the motility.
The motility data may be presented to a user in various manners;
for example, a plot of motility over time may be generated, or
indications of low or abnormal motility may be presented to the
user of the system.
According to an embodiment of the invention motility analysis data
is examined for at least one parameter, the parameter is compared
to a reference and at least one condition in the GI tract is
deduced from the comparison.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood and appreciated more fully
from the following detailed description taken in conjunction with
the drawings in which:
FIG. 1 is a schematic illustration of an in vivo imager system,
according to one embodiment of the present invention;
FIGS. 2A and 2B show a simplified series of images, which may be
captured by the vivo imager system of FIG. 1;
FIG. 3 depicts a motility chart produced by the system of FIG. 1,
according to one embodiment of the present invention;
FIG. 4 is a flow chart showing the steps for determining the
motility of a device recording images from a body lumen according
to an exemplary embodiment of the present invention; and
FIGS. 5A and 5B are histograms used to calculate motility according
to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the following description, various aspects of the present
invention will be described. For purposes of explanation, specific
configurations and details are set forth in order to provide a
thorough understanding of the present invention. However, it will
also be apparent to one skilled in the art that the present
invention may be practiced without the specific details presented
herein. Furthermore, well known features may be omitted or
simplified in order not to obscure the present invention.
The present invention relates to a method and system for analyzing
motility within a GI tract and for displaying motility to a user
such as a health professional, who may use such data to, for
example, diagnose pathologies. In an exemplary embodiment of the
present invention, the motility of a capsule or other vehicle,
which is propelled through the GI tract by the natural action of
the GI tract is measured, giving an indication of the motility in
the GI tract, in different portions of the GI tract. In one
embodiment, the motility of the vehicle is calculated via an
analysis of sequential images captured by the vehicle; the greater
the difference between sequential images, the greater the
motility.
Reference is made to FIG. 1, which shows a schematic diagram of an
in vivo imaging system according to one embodiment of the present
invention. In an exemplary embodiment, the system comprises a
capsule 40 having an imager 46, for capturing images, an
illumination source 42, for illuminating the body lumen, and a
transmitter 41, for transmitting image and possibly other
information to a receiving device. An optical system (not shown),
including, for example, lenses or mirrors, may aid in focusing
reflected light onto the imager 46. The capsule 40 is swallowed by
a patient and preferably traverses the patient's GI tract. In
alternate embodiments the capsule 40 may have different
configurations and include other sets of components.
Preferably, while the capsule 40 traverses a patient's GI tract,
the capsule 40 transmits image and possibly other data to
components located outside the patient's body, which receive and
process the data. Preferably, located outside the patient's body in
one or more locations, are an image receiver 12, preferably
including an antenna or antenna array, an image receiver storage
unit 16, a data processor 14, a data processor storage unit 19, and
an image monitor 18, for displaying, inter alia, the images
recorded by the capsule 40 and motility information. In one
embodiment, the image receiver 12 and image receiver storage unit
16 are small and portable, and are worn on the patient's body
during recording of the images. Optionally, data processor 14, data
processor storage unit 19 and monitor 18 may be part of a personal
computer or workstation, which includes standard components such as
processor 14, a memory, a disk drive, and input-output devices,
although alternate configurations are possible.
Data processor 14 may include any standard data processor, such as
a microprocessor, multiprocessor, accelerator board, or any other
serial or parallel high performance data processor. Image monitor
18 may be a computer screen or a conventional video display, but
may, in addition, be a printer or any other device capable of
providing an indication of image and/or position data.
Preferably, the imager 46 is a suitable CMOS camera, such as a
"camera on a chip" type CMOS imager specified by Given Imaging Ltd.
of Israel and designed by Photobit Corporation of California, USA.
In alternate embodiments, the imager 46 may be, for example, a CCD.
The illumination source 42 may be, for example, a light emitting
diode.
In operation, imager 46 captures images and sends data representing
the images to transmitter 41, which transmits images to image
receiver 12 using, for example, electromagnetic radio waves. Image
receiver 12 transfers the image data to image receiver storage unit
16. After a certain period of time of data collection, the image
data stored in storage unit 16 is sent to data processor 14 or data
processor storage unit 19. For example, the image receiver storage
unit 16 may be taken off the patient's body and connected to the
personal computer or workstation which includes the data processor
14 and data processor storage unit 19 via a standard data link,
e.g., a serial or parallel interface of known construction. The
image data is then transferred from the image receiver storage unit
16 to the data processor storage unit 19. Data processor 14
analyzes the data and provides the analyzed data to the image
monitor 18, where a health professional views, for example, the
image data and motility information.
The image data collected and stored may be stored indefinitely,
transferred to other locations, or manipulated or analyzed. A
health professional may use the images to diagnose pathological
conditions of the GI tract, and, in addition, the system may
provide information about the location of these pathologies. While,
using a system where the data processor storage unit 19 first
collects data and then transfers data to the data processor 14, the
image data is not viewed in real time, other configurations allow
for real time viewing. In such systems, image motility may be
calculated and displayed in real time.
The image monitor 18 presents the image data, preferably in the
form of still and moving pictures, and in addition may present
other information. In an exemplary embodiment, such additional
information may include, but is not limited to, absolute time
elapsed for the current image being shown and the relative or
absolute motility of the capsule 40, over the course of the
capsule's travel through the GI tract, and/or at the time
corresponding to the current image being displayed. Absolute time
elapsed for the current image being shown may be, for example, the
amount of time that elapsed between the moment the capsule 40 was
first activated and the image receiver 12 started receiving
transmissions from the capsule 40, and the moment that the current
image being displayed was captured. Various methods may be used to
display the motility of the capsule 40; such methods are discussed
below. In an exemplary embodiment, the various categories of
information are displayed in windows. Multiple monitors may be used
to display image and other data.
Preferably, the image data recorded and transmitted by the capsule
40 is digital color image data, although in alternate embodiments
other image formats may be used. In an exemplary embodiment, each
frame of image data includes 256 rows of 256 pixels each, each
pixel including data for color and brightness, according to known
methods. For example, in each pixel, color may be represented by a
mosaic of four sub-pixels, each sub-pixel corresponding to
primaries such as red, green, or blue (where one primary is
represented twice). The brightness of the overall pixel is recorded
by a one byte (i.e., 0-255) brightness value. Preferably, images
are stored sequentially in data processor storage unit 19. The
stored data is comprised of one or more pixel properties, including
color and brightness.
While, preferably, information gathering, storage and processing is
performed by certain units, the system and method of the present
invention may be practiced with alternate configurations. For
example, components providing for motility analysis may be located
inside a capsule or, alternately, on a portable device worn on the
patient. Furthermore, the components gathering image information
need not be contained in a capsule, but may be contained in any
other vehicle suitable for traversing a lumen in a human body, such
as an endoscope, stent, catheter, needle, etc.
The in vivo imager system may collect a large volume of data, as
the capsule 40 may take several hours to traverse the GI tract, and
may record images at a rate of, for example, two images every
second, resulting in the recordation of tens of thousands of
images. The series of still images collected may later be presented
as still images or as a moving image of the traverse of the GI
tract. The image recordation rate (or frame capture rate) may be
varied; for example, the image recordation rate may be varied based
on capsule motility. While in the GI tract, the capsule 40
undergoes intermittent motion with long residence time at some
positions. These periods of long residence may be normal or can be
due to pathologies, such as blockages, within the digestive tract.
The system and method of the present invention aids health
professionals in monitoring the capsule motion and in diagnosing
and locating, for example, areas of blockage. In addition, changes
in motility may be indicative of a normal condition such as the
passage of the capsule 40 from one section of the GI tract to
another, and thus the system and method of the present invention
may use motility data to determine the position of the capsule 40
or other diagnostic device.
In an exemplary embodiment, each image P.sub.i in the data stream
of images is compared to **its predecessor image P.sub.i-I (or to
other previous image P.sub.i-n) to determine the motility of the
capsule 40 during the time between the capture of the two images.
Various methods of determining motility based on image comparison
may be used. In an exemplary embodiment, the system and method
analyze image similarity to obtain a measure of motility. It can be
assumed that the more similar two compared images are, the slower
the movement of the capsule 40 between the times the two images are
captured. In an extreme situation--if the two compared images are
identical--it can be assumed the capsule 40 has not moved between
the times the two images were captured. If two compared images
differ greatly, it is an indication that the capsule 40 was moving
quickly between the times of capture of the images. This concept is
illustrated further in FIGS. 2A and 2B.
FIGS. 2A and 2B show a simplified series of images, which may be
captured by the vivo imager system of FIG. 1. Referring to FIGS. 2A
and 2B, a comparison of images provides information about the speed
of the capsule 40. In FIG. 2A, several consecutive images are shown
in which a specific point X is located in approximately the same
location within each of the images. In FIG. 2B, the same point X is
located in varying positions within the images, taken over the same
period of time. It can be inferred that the images shown in FIG. 2A
were taken by an imager whose position did not change by much
between the times each image was taken, and thus which had
relatively low motility. It can be inferred that the images shown
in FIG. 2B were taken by an imager which is moving more
rapidly.
Preferably, data processor storage unit 19 stores a series of
images recorded by a capsule 40. The images may be combined
consecutively to form a moving image of the images the capsule 40
recorded as it moved through a patient's GI tract. This moving
image may be displayed in a window on monitor 18. The moving image
may be frozen to view one frame, speeded up, or reversed; sections
may be skipped; or any other method for viewing an image may be
applied to the moving image. While the following discussion relates
to the case where data from a capsule 40 is stored for later use,
the system and method of the present invention may be used with
systems allowing for real time viewing of image data.
In an exemplary embodiment, to determine the motility of the
capsule 40 at various points during its journey through the GI
tract, data processor 14 first receives image data from data
processor storage unit 19. Data processor 14 then compares each
image P.sub.i in the data stream to its predecessor image P.sub.i-I
(or P.sub.i-n) to determine the motility of the capsule 40 during
the time between the capture of the two images.
The comparison of images may be made on a pixel-by pixel basis or,
alternatively, on a pixel cluster basis. In alternate embodiments,
images may be compared without division into sections such as
pixels or clusters. In an exemplary embodiment, the 256.times.256
pixel grid of each image is divided into a 32.times.32 grid of
pixel clusters, to form 1,032 clusters. In alternate embodiments,
other methods of dividing an image may be used. Based on the
comparison of the two images, data processor 14 calculates the
relative motility for the capsule 40 that captured the images for
the time period between the capture of the two images. In an
exemplary embodiment, the resulting motility value at a certain
point is a relative number on a certain scale, which indicates the
motility of the capsule 40 relative to other points in the
capsule's traverse of the GI tract. In alternate embodiments,
absolute motility may be calculated.
The motility calculation is repeated for all or a set of images in
the series of images, and a series of motility values is generated.
The resulting motility values may be presented to the user in
various manners. Preferably, the monitor 18 includes a window
displaying an image frame or a moving image, a window showing the
absolute time elapsed in the image series for the frame being
displayed (or the current point in the moving image), and a window
including a chart of the relative motility of the capsule 40
plotted against time. An indication may be provided on the display
on monitor 18 connecting certain motility values, or regions having
low motility or certain motility patterns, to images or sections of
the moving image. The user may be able to indicate certain motility
values or a portion of the motility chart or plot by, for example,
clicking with a mouse, and have displayed the corresponding still
or moving image.
Additional windows may display other data. For example, the
position of the capsule 40 as it traverses the GI tract may be
graphed as a two-dimensional rendering of the three-dimensional
path; such data may be combined with or linked to image or motility
data. Areas of low motility, or areas of altered or abnormal
patterns of motility, may be indicated on such a capsule path
representation by using, for example, color changes or labels.
In one embodiment, a spectral analysis of the motility data may be
performed, and the spectral analysis may be presented to the user
or may be used for diagnostic or other purposes. In a normal human
GI tract, peristaltic waves are typically generated with some
repetition. A spectral analysis, according to known methods, of the
peristaltic waves of different time periods or sections of the
series of motility data, may be performed and, for example,
presented to the user. Such a spectral analysis may present, for
example, the frequency of repetition of peristaltic waves at
different times or positions in a vehicle's travel through the GI
tract. In alternate embodiments, other visual indications of
motility may be provided.
According to one embodiment of the invention, motility data can be
examined for at least one parameter or measurement that may be
presented as, for example, a specific pattern or representation of
a pattern in a spectral analysis of the motility data or a specific
repetition or representation of a repetition of peristaltic waves.
The parameter, possibly represented by a pattern or specific
patterns, can be compared to a reference, such as a parameter value
in a normal or healthy individual or a specific pattern typical of
a pathological condition in the GI tract. The comparison results
can indicate, for example, a prevailing condition (or conditions)
in the GI tract, thereby providing a diagnostic tool for
identifying conditions in the GI tract. For example, a spectral
analysis may be performed on the motility of an in-vivo device. The
spectral analysis may be represented, for example, as a graph of
movement waves over time; other ways of representing a spectral
analysis may be used. A pattern matching module (for example,
processor 14 operating according to software) may seek to match the
recorded spectral analysis to spectral analyses corresponding to
various conditions, and a match or near match may be reported to a
user.
FIG. 3 depicts a motility chart produced, for example, by the
system of FIG. 1, according to one embodiment of the present
invention. The plot or chart 100 includes a time axis 102, a
relative motility axis 104, and a motility plot or graphing 106.
Preferably, if the health 20 professional indicates a certain point
along the motility chart, using, for example, a pointing device
such as a mouse, the corresponding image appears in the image
window. While, in an exemplary embodiment, the relative motility is
expressed in arbitrary units (for example, 0 to 10, adjusted
logarithmically), other methods of expressing motility may be used,
and absolute motility may also be expressed.
The chart 100 may include indications of low motility 108, which
may be, for example, marks or colored or shaded regions indicating
areas where motility is low enough to warrant investigation by a
health professional. The data processor 14 may filter for certain
patterns of motility, where such patterns may commonly indicate
either normal conditions, such as passage between areas of the GI
tract, or pathological conditions. Such conditions may be labeled
on the motility chart. In response to such indications of low
motility, the health professional may click or otherwise indicate
the area on the motility chart in question, and view images (still
or moving) of the corresponding area in the GI tract.
Any number of methods may be used to analyze the image data to form
motility data. For example, motility analysis may be based on a
calculation of the difference in a given property between
corresponding pixels of two, not necessarily consecutive, frames; a
calculation of the cross-correlation function between two, not
necessarily consecutive, frames; a calculation of the changes of
local statistical distributions in two, not necessarily
consecutive, frames; or a calculation of the changes between
corresponding local statistical distributions in two, not
necessarily consecutive, frames. Local statistical distributions
may include, but are not limited to, the mean, the variance, or the
standard deviation of pixel clusters.
In an exemplary embodiment, each image in a pair of images being
compared is divided into a number of sections. Each section in the
first image is compared to the corresponding section in the second
image. The variance of the difference of the brightness for the two
sections, normalized by the number of sections, is calculated. The
variance is used to ascertain the relative motility of the vehicle
capturing images, which in an exemplary embodiment is capsule
40.
Reference is now made to FIG. 4, a flow chart showing the steps for
determining the motility of a device recording images from a body
lumen according to an exemplary embodiment of the present
invention.
In step 200, image data is recorded by the capsule 40 and
transmitted to the data processor storage unit 19. In step 202,
data processor 14 receives from data processor storage unit 19
images P.sub.i and P.sub.i+x, where x is usually, but not
necessarily, 1. If the stream of images is too lengthy or rapid, a
decimation may be performed and non-adjacent images may be
compared, e.g., image P.sub.i and P.sub.i+x, where x>1.
In step 204, data processor 14 may divide each of the two images
into pixel clusters, sections or cells. In an exemplary embodiment,
each image Pi is divided into 1024 clusters A.sub.i (m,n), where
1<m<32 and 1<n<32.
In step 206, data processor 14 calculates the average intensity
I.sub.Ai(m,n) of each cluster A.sub.i (m,n) of each of image
P.sub.i and P.sub.i+x. Preferably, the intensity value for a
cluster is the average of the brightness values for the pixels in
the cluster. A matrix of the intensities of the clusters may be
formed for each image. Alternate methods of calculating intensity
may be used; for example, color data may be used to compare
images.
In step 208, data processor 14 determines the absolute value
D.sub.i (m,n) of the difference of the average intensities I of
A.sub.i (m,n) and A.sub.i+x (m,n) of corresponding clusters A(m,n)
in the frames P.sub.i and P.sub.i+x. D.sub.i (m,n) is defined
as:
A matrix of the absolute values of differences is formed, one value
being generated for each cluster compared.
In step 210, data processor 14 determines the average difference
(Diff) between the two images. In an exemplary embodiment, the
average difference is calculated by first subtracting from each
absolute value in the matrix created in step 208 the average value
of all the differences in the matrix, summing the resulting values,
taking the square root of the resulting sum, and dividing by the
number of the differences in the matrix (in an exemplary embodiment
1024). This may be expressed by the formula: ##EQU1##
where Diff corresponds to the average of the values in the
difference matrix.
In an exemplary embodiment, the resulting average difference is a
value from 0 to U, where U is an arbitrary upper limit which
depends upon the input parameters. A low average difference
indicates that the measured value (in an exemplary embodiment,
brightness) varies little between the compared frames, and a high
value of the average difference indicates that the measured value
varies a large amount. A low difference is an indication of low
motility, as, if the capsule 40 is not moving quickly, the images
in the two compared frames will not vary by a large amount.
In step 212, if more frames exist in the image stream, data
processor 14 returns to step 202. If no more frames exist, data
processor 14 proceeds to step 214. At this point, the difference
data exists as a series of difference values, one for each frame
pair analyzed, preferably X-1 variances, where X is the number of
frames analyzed.
In step 214, data processor 14 may normalize or decimate the
resulting difference data to an arbitrary scale. This normalized
data represents the relative motility of the capsule 40. In an
exemplary embodiment, each difference datum, represented as a value
from 0-U, is normalized to a number between 0 and 10; other ranges
may be used. The normalization process may be linear or may be
non-linear--for example, a logarithmic function may be used. In
alternate embodiments, other normalization or decimation functions
may be used; for example, the difference data may be translated to
a set of integers. During normalization, various functions, such as
logarithmic functions, may be applied to the data.
In step 216, data processor 14 provides an indication of motility
for the capsule 40. In an exemplary embodiment, data processor 14
creates a plot or graph of relative motility over time for display
on the monitor 18 using the normalized values created in step 214.
Data processor 14 may augment the graph with indications of low
motility or indications of certain conditions. For example,
sections of the graph where motility falls below a certain
threshold may be marked in a certain color or pattern, or may be
otherwise labeled.
In alternate embodiments, other methods of analyzing the image data
to form motility data may be used. For example, for each frame
pair, data processor 14 may organize the difference values D.sub.i
(k,l) into a chart, for example, a histogram, as shown in FIGS. 5A
and B. FIGS. 5A and B depict histograms used to calculate motility
according to an embodiment of the present invention. Referring to
FIGS. 5A and B, the absolute value D.sub.i (m,n) of the difference
is plotted on the x-axis of the histograms and the number of
corresponding pairs of cells, A.sub.i (m,n) and A.sub.i+x (m,n),
which have a difference of magnitude D.sub.i (k,l), is plotted on
the y-axis. The histogram of in FIG. 5A represents a histogram of
cells in relatively similar frames, while the histogram of FIG. 5B
shows a histogram of cells in significantly different frames. It
should be readily apparent that if two images are similar, the
histogram of the differences in the cells of these images are
concentrated at low values of D.sub.i (m,n). It should also be
readily apparent that the center of mass CM.sub.a (the average
difference between the two images) of the histogram shown in FIG.
5A has a smaller value of D than the center of mass CM.sub.b of the
histogram shown in FIG. 5B, and corresponds to a slower moving
capsule 40. To calculate the difference between the two frames,
processor 14 determines the centers of mass CM of the histograms
corresponding to the two frames, and creates a difference value
based on the location of the CM. In another embodiment image
analysis may be used to determine the location of the capsule 40 in
vivo (for example by identifying image parameters that are typical
to a specific region in the GI tract) and the position information
together with known factors; either the time that has elapsed
during the translocation of the capsule 40 or the velocity of the
capsule 40 along its path, can be used to calculate the motility.
Similarly, the location of the capsule may be determined by other
known methods and the location information can be used to calculate
motility.
In alternate embodiments, methods of measuring motility may be used
which are not based on image analysis. For example, the capsule 40
may include an accelerometer, which determines the instantaneous
acceleration of capsule 40 as it moves through the GI tract. An
integrator may convert the acceleration data to velocity data, and
this velocity data may be used by the data processor to determine
motility. Alternately, a pressure sensor or shear gauge attached to
the capsule 40 may detect peristaltic induced pressure or movement
exerted by the walls of the small intestine. The relationship
between pressure and velocity may be determined empirically, and
then utilized to determine the velocity or relative velocity of the
capsule 40. A sensor in the capsule 40 may detect movement relative
to an artificially induced magnetic field, which is generated in
the area of the patient's GI tract. The magnetic field induces a
current in a coil in the sensor, whose magnitude is a function of
the velocity of the coil through the field. Data on the induced
current is converted to motility information. Further, external
sensors may also be used, such as a Doppler ultrasound unit, which
continuously tracks the capsule 40. Additionally, the receiver 12,
which, according to one embodiment is adapted to receive RF signals
from the transmitter 41, may be used to monitor the intensity of
the transmitted signal, whereas signals of unchanging intensities
indicate that the transmitter 41 (and hence the capsule 40) is
unmoving and signals of different intensities indicate that the
transmitter 41 is moving. One or more of the above methods, or
other methods, may be combined to provide a determination of
capsule motility.
It will be appreciated by persons skilled in the art that the
present invention is not limited by what has been particularly
shown and described hereinabove. Rather the scope of the invention
is defined by the claims that follow:
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